Research is proposed to characterize the type and amount of histones and other proteins associated with different regions of the DNA in the genome of SV40 variants which contain host cell information will also be studied. Deoxyribonucleoprotein complexes from isolated virions and from the nuclei of infected cells will be investigated. This investigation is undertaken to (1) provide insight into the processes of DNA packaging and uncoating in SV40 infection and (2) evaluate SV40 nucleoproteins as models for chromatin structure and function. Viral nucleoproteins will be stabilized by introducing reversible chemical cross-links and then digested with restriction endonucleases. Nucleoprotein fragments will be recovered, the cross-links cleaved, and the DNA and protein components analyzed by electrophoretic methods. Emphasis is placed on analyzing SV40 variants presently available, and a procedure is outlined for enzymatic construction of additional SV40 variants containing cellular information from diverse regions of the host genome. BIBLIOGRAPHIC REFERENCES: Nathans, D., Lai, C-J., Scott, W. A., Brockman, W.W., and Adler, S. P. "Construction and Biological Activities of Deletion Mutants of Simian Virus 40". Miami Winter Symposium, in press, (1977). Scott, W. A. and Werner, R. (eds.) "Molecular Cloning of Recombinant DNA" Miami Winter Symposium, Academic Press, New York, (1977), in press.